Tridimensional Geometric Modeling of the Breast

Breast cancer is the most common cancer in France. Its screening and diagnosis use mammography, ultrasound and MRI. These imaging only show the topography of the tumors in the breast volume in two dimensions (2D). The surgeon must then mentally reconstruct the three-dimensional (3D) anatomy of the breast before planning the surgery.The use of a personalized 3D model of the breast would be very useful to help the surgeon to better understand the three-dimensional localization of the tumors in the operative position and thus to better plan the incisions and the dissection of the breast tissue, preserving the maximum of healthy tissue but also being more relevant in the oncological aspect.

This could be achieved with the help of a 3D biomechanical model of the breast which should ideally integrate the subject-specific mechanical properties of all the tissue structures of the breast. However, obtaining a model of the breast is very difficult due to the complexity and diversity of the 3D geometry of the structures and their highly heterogeneous mechanical character. All breast tissues (skin, connective tissue, mammary gland, fat, pectoral muscle) must be modeled. For this, their mechanical behavior must be known. As biomechanical properties vary according to ex-vivo and in-vivo conditions, it is important to obtain in-vivo measurements.

The biomechanical properties of the breast skin have been little studied. The integration of the mechanical parameters of the skin would thus clearly increase the robustness of a 3D model.

Some studies have focused on skin elasticity, mainly on the arms and face. Several non-invasive measurement techniques of the biomechanical properties of the skin have been tested: suction test, torsion test, bi-axial test, and multi-axial test. These techniques may be dependent on the experimental conditions: tension application technique, probe size, skin thickness, ... Among these procedures, suction tests are considered as a reference technique, non-invasive and easy to use, for the measurement of skin elasticity.

The mobility and deformation of the breast skin make it difficult to obtain accurate measurements of biomechanical properties. Sutradhar et al studied these properties in 23 women: variations in elasticity were found for different regions of the breast; lying or standing did not appear to have an impact. In 2016, Coltman et al conducted a study on breast skin elasticity and thickness involving 339 women. Regarding factors that may influence skin elasticity, Coltman et al found a decrease in skin elasticity with age. This effect was not found in the study by Sutradhar et al. A study of 15 women showed a variation in skin elasticity of the breast according to the cycle and whether or not they were taking contraception.Main objective:

To perform a pilot evaluation of the performance of the biomechanical model by integrating the biomechanical characteristics of the skin and the collagenous architecture of the breast, during the transition from prone to supine or lateral position.

Secondary Objectives:

To describe the values of skin elasticity and thickness at different points of the breast, in women in the general population To search for clinical factors predictive of elasticity and skin thickness To carry out a pilot description of the collagen architecture of the breast

Participation in this study will be offered to all patients consulting the gynecology-obstetrics department of the Montpellier University Hospital and meeting the inclusion criteria-Visit 1: Inclusion and measurement of skin thickness and elasticity:

Inclusion will take place during the follow-up consultation in the obstetrics gynecology department of the Montpellier University Hospital. The patient's written consent will be obtained after a reflection period at the end of the consultation. Measurements of elasticity and thickness will then be performed for each of the 200 patients. Skin elasticity: The patient will be installed in dorsal decubitus position, with her arms at her sides on an examination table. Measurements will be performed at 3 sites on one of the two breasts: at the areola, above the areola and below. The measurements will be performed by a single gynecologist in the gynecology department using a cutometer provided by laboratory of Grenoble. It has just been used by the Dutch Cancer Institute in Amsterdam to measure the elasticity of the tongue in a clinical study including 10 patients. Three measurements will be performed at each site. One measurement corresponds to a 10-second suction time (progressive rise of the depression) followed by 5 seconds of relaxation of the measurement site.

The duration of these measurements (installation of the patient - installation of the material - realization of the measurements) will be approximately 15 minutes.

Skin thickness: The measurement of skin thickness will be performed using an ultrasound device available in the obstetrics and gynecology consultation department. The measurement will be performed at 3 sites. The duration of the measurements will be of approximately 10 minutes. Adverse events will be collected at the end of the measurements.

-Visit 2: Within 3 weeks after the first visit. Among the 200 patients, 10 patients who should benefit from a breast MRI as part of their follow-up, will have a breast MRI in 3 different positions: prone (standard protocol) and two additional acquisitions (as part of the research) in dorsal and right lateral decubitus. This examination will be scheduled in t the Lapeyronie Hospital.

Inclusion criteria

• Female
• Up to 18 years old
• Understanding and acceptance of the protocol

Exclusion criteria

• Person protected by law under guardianship or curatorship
• Failure to obtain free, informed and written consent after a reflection period
• A patient who is not a member or beneficiary of a national health insurance system
• Patient with a skin disease or a skin lesion
• Person deprived of liberty by judicial or administrative decision
• Application of a cream on the skin within 12 hours before the measurements